//=================================================================================================
// Copyright (c) 2011, Stefan Kohlbrecher, TU Darmstadt
// All rights reserved.

// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
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//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above copyright
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//     * Neither the name of the Simulation, Systems Optimization and Robotics
//       group, TU Darmstadt nor the names of its contributors may be used to
//       endorse or promote products derived from this software without
//       specific prior written permission.

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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//=================================================================================================

#ifndef __GridMapCacheArray_h_
#define __GridMapCacheArray_h_

#include <Eigen/Core>

class CachedMapElement
{
public:
    float val;
    int index;
};

/**
 * 网格缓存，类似于计算机的cache，保存最近访问过的网格的概率值（非logOddsVal值）。
 * 避免重复访问同一网格时，重复计算其概率值。（Cell中只保存了logOddsVal值）
 *
 *
 * Caches filtered grid map accesses in a two dimensional array of the same size as the map.
 */
class GridMapCacheArray
{
public:
    /**
   * Constructor
   */
    GridMapCacheArray()
        : cacheArray(0), arrayDimensions(-1, -1)
    {
        currCacheIndex = 0;
    }

    /**
   * Destructor
   */
    ~GridMapCacheArray()
    {
        deleteCacheArray();
    }

    /**
   * Resets/deletes the cached data
   * 只有当  CachedMapElement.index == currCacheIndex 时，元素有效
   * 改变currCacheIndex的值，使当前cache内所有元素无效
   */
    void resetCache()
    {
        currCacheIndex++;
    }

    /**
   * Checks wether cached data for coords is available. If this is the case, writes data into val.
   * @param coords The coordinates
   * @param val Reference to a float the data is written to if available
   * @return Indicates if cached data is available
   */
    bool containsCachedData(int index, float &val)
    {
        const CachedMapElement &elem(cacheArray[index]);

        if (elem.index == currCacheIndex)
        {
            val = elem.val;
            return true;
        }
        else
        {
            return false;
        }
    }

    /**
   * Caches float value val for coordinates coords.
   * @param coords The coordinates
   * @param val The value to be cached for coordinates.
   */
    void cacheData(int index, float val)
    {
        CachedMapElement &elem(cacheArray[index]);
        elem.index = currCacheIndex;
        elem.val = val;
    }

    /**
   * Sets the map size and resizes the cache array accordingly
   * @param sizeIn The map size.
   */
    void setMapSize(const Eigen::Vector2i &newDimensions)
    {
        setArraySize(newDimensions);
    }

protected:
    /**
   * Creates a cache array of size sizeIn.
   * @param sizeIn The size of the array
   */
    void createCacheArray(const Eigen::Vector2i &newDimensions)
    {
        arrayDimensions = newDimensions;

        int sizeX = arrayDimensions[0];
        int sizeY = arrayDimensions[1];

        int size = sizeX * sizeY;

        cacheArray = new CachedMapElement[size];

        for (int x = 0; x < size; ++x)
        {
            cacheArray[x].index = -1;
        }
    }

    /**
   * Deletes the existing cache array.
   */
    void deleteCacheArray()
    {
        delete[] cacheArray;
    }

    /**
   * Sets a new cache array size
   */
    void setArraySize(const Eigen::Vector2i &newDimensions)
    {
        if (this->arrayDimensions != newDimensions)
        {
            if (cacheArray != 0)
            {
                deleteCacheArray();
                cacheArray = 0;
            }
            createCacheArray(newDimensions);
        }
    }

protected:
    CachedMapElement *cacheArray; ///< Array used for caching data.
    int currCacheIndex;           ///< The cache iteration index value

    Eigen::Vector2i arrayDimensions; ///< The size of the array
};

#endif
